Preparation of titanosilicate zeolite TS-1

ABSTRACT

A method is disclosed for preparing crystalline titanosilicate zeolite TS-1 from a reaction mixture containing only sufficient water to produce zeolite TS-1. In one embodiment, the reaction mixture is self-supporting and may be shaped if desired. In the method, the reaction mixture is heated at crystallization conditions and in the absence of an added external liquid phase, so that excess liquid need not be removed from the crystallized product.

FIELD OF THE INVENTION

The present invention relates to a process for producing crystallinetitanosilicate zeolite TS-1 from a reaction mixture which contains onlysufficient water to form zeolite TS-1. As used herein, the terms“titanosilicate zeolite TS-1”, “zeolite TS-1”, or simply TS-1 refers tozeolites having the framework topology of ZSM-5 which contain titaniumatoms in their framework structure.

BACKGROUND

Prior art methods of preparing crystalline zeolite TS-1 typicallyproduce finely divided crystals which must be separated from an excessof liquid in which the zeolite is crystallized. The liquid, in turn,must be treated for reuse or else be discarded, with potentiallydeleterious environmental consequences. Preparing commercially usefulcatalytic materials which contain the powdered zeolite also normallyrequires additional binding and forming steps. Typically, the zeolitepowder as crystallized must be mixed with a binder material and thenformed into shaped particles or agglomerates, using methods such asextruding, agglomeration, and the like. These binding and forming stepsgreatly increase the complexity of catalyst manufacture involvingzeolitic materials. The additional steps may also have an adverse effecton the catalytic performance of the zeolite so bound and formed.

U.S. Pat. No. 3,094,383, issued Jun. 18, 1963 to Dzierzanowski et al.,discloses a method for making type A zeolites in the form of coherentpolycrystalline aggregates by forming reaction masses consisting of amixture of sodium aluminate, a siliceous material and water, wherein theH₂O/Na₂O mole ratio is 5 to 25. The mass is aged while maintaining itout of contact with an external aqueous liquid phase while preventingthe mass from dehydrating. The aging step can include maintaining themass at 100° F. (38° C.) for, e.g., 18 hours, followed by heating at200° F. (93° C.) for, e.g., 24 hours.

U.S. Pat. No. 3,119,659, issued Jan. 28, 1964 to Taggart et al.,discloses a method for producing an aluminosilicate zeolite in apreformed body by providing an unreacted preformed body containing areactive kaolin-type clay and alkali metal hydroxide, and reacting thepreformed body in an aqueous reaction mixture until crystals of thezeolite are formed in the body. The aggregate of the preformed body andthe aqueous reactant mixture has a H₂O/Na₂O mole ratio of at least 20.

U.S. Pat. No. 4,058,586, issued Nov. 15, 1977 to Chi et al., discloses amethod for preparing zeolitic aluminosilicates, particularly those thatare characterized by pores in the 4 to 10 Angstrom sizes that aredesignated Zeolites A and X, in which compacts of Zeolites A and X,metakaolin clay mixture undergo crystallization at a temperature of 200°to 700° F. (93° to 371° C.). The crystallization is carried out in acalciner or other drying equipment. Normally, the formed particlesfurnish all of the liquid needed for crystallization, though steam maybe added during the crystallization process.

WO 94/13584, published Jun. 23, 1994, discloses a method for preparing acrystalline aluminosilicate zeolite from a reaction mixture containingonly sufficient water so that the reaction mixture may be shaped ifdesired. In the method, the reaction mixture is heated atcrystallization conditions and in the absence of an external liquidphase, so that excess liquid need not be removed from the crystallizedmaterial prior to drying the crystals.

GB 2,160,517 A, published Dec. 24, 1985, relates to a preformedsynthetic zeolite selected from the group consisting of Y, omegazeolite, offretite, erionite, L zeolite and ferrierite whose Si/Alatomic ratio ranges from 1.5 to 100, the preformed zeolite beingobtained from a preformed aluminosilicic material whose Si/Al atomicratio is lower than that of the product and ranges from 0.5 to 90 bytreating the material with a silica-containing product in the presenceof at least one organic or inorganic base.

U.S. Pat. No. 5,558,851, issued Sep. 24, 1996 to Miller, discloses amethod for preparing a crystalline aluminosilicate zeolite from areaction mixture containing only sufficient water so that the reactionmixture may be shaped if desired. The reaction mixture is heated undercrystallization conditions and in the absence of an external liquidphase, so that excess liquid need not be removed from the crystallizedmaterial prior to drying the product. U.S. Pat. No. 5,558,851 isincorporated herein by reference in its entirety.

Titanosilicate zeolite TS-1 is known. See, for example, U.S. Pat. No.4,410,501, issued Oct. 18, 1983 to Taramasso et al. in which TS-1 and amethod for making it are disclosed. U.S. Pat. No. 4,410,501 isincorporated by reference herein in its entirety.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method forpreparing crystalline titanosilicate zeolite TS-1, said methodcomprising:

-   -   (A) preparing a reaction mixture comprising at least one active        source of silica and at least one active source of titanium        oxide in amounts sufficient to produce zeolite TS-1, at least        one quaternary ammonium cation capable of forming crystals of        TS-1 and sufficient water to produce zeolite TS-1; and    -   (B) heating said reaction mixture under crystallization        conditions and in the absence of an added external liquid phase        for sufficient time to form crystals of zeolite TS-1.        The method can employ a reaction mixture having a water/silica        molar ratio during crystallization of no greater than about 3,        for example between about 0.7 and about 2.        The reaction mixture can have the following molar composition        ranges:

SiO₂/TiO₂ =  25-500 OH⁻/SiO₂ = 0.04-0.30 H₂O/SiO₂ = 0.5-3   Q/SiO₂ =0.04-0.30where Q is the quaternary ammonium cation. The reaction mixture can alsohave the following molar composition ranges:

SiO₂/TiO₂ =  30-150 OH⁻/SiO₂ = 0.06-0.15 H₂O/SiO₂ = 0.7-2   Q/SiO₂ = 0.06-0.15.The quaternary ammonium compound can a tetraalkylammonium cation such asa tetrapropylammonium cation.

The present invention further provides a method for preparingcrystalline titanosilicate zeolite TS-1, said method comprising:

-   -   (A) preparing a reaction mixture comprising at least one active        source of silica and at least one active source of titanium        oxide in amounts sufficient to produce zeolite TS-1, and        sufficient water to shape said mixture;    -   (B) forming said reaction mixture into a shape; and    -   (C) heating said reaction mixture under crystallization        conditions and in the absence of an added external liquid phase        for sufficient time to form crystals of zeolite TS-1.        The amount of water can be that which is sufficient to make the        reaction mixture self-supporting. The method can employ a        reaction mixture having a water/silica molar ratio during        crystallization of no greater than about 3, for example between        about 0.7 and about 2. The reaction mixture can have the        following molar composition ranges:

SiO₂/TiO₂ =  25-500 OH⁻/SiO₂ = 0.04-0.30 H₂O/SiO₂ = 0.5-3   Q/SiO₂ =0.04-0.30where Q is the quaternary ammonium cation. The reaction mixture can alsohave the following molar composition ranges:

SiO₂/TiO₂ =  30-150 OH⁻/SiO₂ = 0.06-0.15 H₂O/SiO₂ = 0.7-2   Q/SiO₂ = 0.06-0.15.The quaternary ammonium compound can a tetraalkylammonium cation such asa tetrapropylammonium cation. The shaped crystalline zeolite can be inthe form of a spherical or cylindrical particle having a cross sectionaldiameter between about 1/64 inch and about ½ inch.

Also provided by the present invention is a reaction mixture compositioncapable of forming crystals of titanosilicate zeolite TS-1, saidcomposition comprising at least one active source of silica and at leastone active source of titanium oxide in amounts sufficient to producezeolite TS-1, at least one quaternary ammonium cation capable of formingcrystals of TS-1 and sufficient water to produce TS-1, said compositionbeing in the form of a self-supporting, shapeable mass.

Further provided in accordance with the present invention is a shaped,binderless catalyst comprising essentially all titanosilicate TS-1 andTS-1 precursors.

The present invention also provides crystalline titanosilicate zeoliteTS-1 having a crystallite size of less than 0.2 micron.

Also provided by the present invention is a process for oxidation ofhydrocarbons comprising contacting said hydrocarbon with hydrogenperoxide in the presence of a catalytically effective amount ofcrystalline, titanosilicate zeolite TS-1 for a time and at a temperatureeffective to oxidize said hydrocarbon, wherein the catalyst is in theform of a binderless, shaped particle comprising essentially all TS-1and TS-1 precursors.

The present invention further provides a process for epoxidation of anolefin comprising contacting said olefin with hydrogen peroxide in thepresence of a catalytically effective amount of a crystalline,titanosilicate zeolite TS-1 for a time and at a temperature effective toepoxidize said olefin, wherein the catalyst is in the form of abinderless, shaped particle comprising essentially all TS-1 and TS-1precursors.

Also provided by the present invention is a process for oxidizingcyclohexane comprising contacting said cyclohexane with hydrogenperoxide in the presence of a catalytically effective amount of acrystalline, titanosilicate zeolite TS-1 for a time and at a temperatureeffective to oxidize the cyclohexane, wherein the catalyst is in theform of a binderless, shaped particle comprising essentially all TS-1and TS-1 precursors.

It is important, in preparing the reaction mixture of the presentprocess, that the amount of water present in the reaction mixture asprepared for the crystallization step be sufficient to produce thezeolite TS-1. Thus, the reaction mixture itself furnishes all the waterneeded to crystallize the zeolite. This amount of water is less than theamount of water required in conventional processes for preparingzeolites. It is an amount which is not substantially greater than thatrequired to produce the zeolite TS-1. For example, the amount of waterused in the present invention is less than that required to dissolve thereaction mixture components, or, if they are not dissolved, less thanthat required to immerse the reaction mixture components in the water.Thus, during the crystallization step according to the present process,there is no separate, added external liquid phase present which must beremoved from the crystallized material at the end of the crystallizationstep by, for example filtering or decanting, prior to drying thecrystals. This absence of an added external liquid phase distinguishesthe present invention from methods for making zeolite TS-1 wherein thezeolite TS-1 crystals are formed from a solution or gel, or where solidreactants are heated in an aqueous solution until crystals of zeoliteTS-1 form.

While it is not a requirement to form the mixture into a shape beforethe mixture is subjected to crystallization conditions, it may bedesired in many cases to do so. In that case, the amount of waterpresent in the reaction mixture is sufficient to form the reactionmixture into a shape, but insufficient to cause the shaped reactionmixture to collapse or “melt”, i.e., once the reaction mixture is formedinto the desired shape containing the desired amount of water, theresulting shape is self-supporting.

Among other factors, the present invention is based on the discovery ofa method for crystallizing zeolite TS-1 from a reaction mixture whichcontains only enough water to form the zeolite TS-1. Further, thezeolite TS-1 prepared by the above described method is made as verysmall crystallites.

DETAILED DESCRIPTION OF THE INVENTION

Description of Zeolite TS-1

Zeolite TS-1 and its X-ray diffraction pattern are disclosed in U.S.Pat. No. 4,410,501, issued Oct. 18, 1983 to Taramasso. It is to beunderstood that by referencing this patent, it is intended thatidentification of zeolite TS-1 be resolved on the basis of its X-raydiffraction pattern. The present invention includes the preparation ofzeolite TS-1 regardless of its silica/titanium oxide mole ratio. Thus,reference to this patent is not to be construed as limiting the presentinvention to the preparation of zeolite TS-1 having the silica/titaniumoxide mole ratios disclosed in that patent. It is the frameworktopology, as identified by the X-ray diffraction pattern, whichestablishes the identity of the zeolite TS-1.

Preparing the Reaction Mixture

The reaction mixture from which and in which the zeolite TS-1 iscrystallized comprises at least one active source of silica, at leastone active source of titanium oxide, a nitrogenated organic base capableof forming crystals of TS-1, and sufficient water to form the zeoliteTS-1. This amount of water is considerably less than that required inconventional processes for preparing zeolite TS-1.

The amount of water required in the reaction mixture of the presentinvention is that amount which is needed to adequately blend themixture. Thus, a reaction mixture is prepared by mixing water withactive sources of the zeolite to form a uniform mass having preferably aheavy paste-like consistency. The active sources will be in a form whichcan be easily blended into a uniform mass, and may be, for example,powders, hydrated particles, or concentrated solutions. Sufficient wateris added to wet all the powders during mixing and kneading of thereaction mixture. Alternatively, sufficient water is added that thepowders may be kneaded into a uniform and generally homogeneous mixturewhich may be shaped. It is not necessary that all of the active sourcesbe readily soluble in water during kneading, since the water added tothe active sources will be insufficient to make a fluid-like mixture.The amount of water added depends on the mixing apparatus and on theactive sources employed. Those familiar with the art can readilydetermine without undue experimentation the amount of liquid required toproperly mix active sources of the zeolite. For example, hydratedsources of the zeolite may require relatively less water, and driedsources may require relatively more. Though it is preferred that themixture be blended and kneaded until the mixture has a uniform,homogeneous appearance, the length of time devoted to kneading themixture is not critical in the present invention.

The water content of the reaction mixture after blending and kneadingmay be further adjusted, for example, by drying or by the addition ofwater. When it desired that the reaction mixture be formed into a shape(such as by extrusion), adjusting the amount of water can facilitateshaping the reaction mixture and ensure that it will be self-supporting,i.e., the shape will not collapse or “melt” due to an excess of water inthe reaction mixture.

Typical sources of silicon oxide (SiO₂) include silicates, silicahydrogel, silicic acid, colloidal silica, fumed silica,tetraalkylorthosilicates silica hydroxides, precipitated silica andclays. Preferred sources of silicon oxide are solid, essentiallyaluminum-free, amorphous silicas. Ultrasil® VN3SP silica available fromDegussa, having an aluminum content less than about 0.2 wt. % aluminumis a preferred source of silicon oxide.

The titanosilicate zeolites of this invention should be free of aluminumin order to perform optimally as oxidation catalysts. It is, however,possible that traces of aluminum may be introduced into the zeolitefrom, e.g., a silica source which contains minor amounts of aluminum. Ifthis occurs, the protons associated with the aluminum should be replacedwith ammonium, alkali metal or alkaline earth cations. Thus, it isimportant that the silica source be as free of aluminum as possible.

Typical sources of titanium include hydrolysable titanium compounds,TiCl₄, TiOCl₂, Ti(alkoxy)₄, tetraalkylorthotitanates (such astetraethylorthotitanate). In addition, coprecipitates comprised of bothsilicon and titanium (such as W. R. Grace's Si—Ti Type III/2) can beused as a starting reagent. A preferred source of titanium isTi(alkoxy)₄, such as Ti(butoxide)₄. The titanium source may be dissolvedin a solvent, such as isopropyl alcohol.

Unlike the preparation of aluminosilicate zeolites, the reaction mixturefor preparing the titanium-containing zeolites of this invention shouldnot contain alkali metal hydroxide. The presence of alkali metal cationsin the reaction mixture can give rise to an undesirable titanium phasein the final product. In addition, all of the hydroxide ions needed inthe reaction mixture are supplied by the structure directing agent(SDA), also sometimes called an organic templating agent.

The SDA's useful in the present invention are quaternary ammoniumcations capable of forming crystals of TS-1. Examples of quaternaryammonium cations include, but are not limited to tetraalkylammoniumcations. Since alkali metals are to be avoided, it is preferred that thecounterion for the quaternary ammonium cation be hydroxide to serve asthe source of hydroxide for the reaction mixture. The tetraalkylammoniumcations include tetrapropylammonium cation (TPA) and tetraethylammoniumcation (TEA). It should be noted that TEA may form crystals with theframework topology of zeolite Beta, so if TEA is used as the SDA it maybe necessary to use it in combination with TPA. The SDA should be usedin an amount sufficient to form crystals of TS-1. This amount will varydepending upon the relative amounts of the other components of thereaction mixture.

The reaction mixture should contain the following components in theamounts indicated (expressed as mole ratios of oxides even though theactual starting materials may not be oxides):

General Preferred SiO₂/TiO₂ =  25-500  30-150 OH⁻/SiO₂ = 0.04-0.300.06-0.15 H₂O/SiO₂ = 0.5-3   0.7-2   Q/SiO₂ = 0.04-0.30 0.06-0.15where Q is the SDA.Forming the Shapes

One advantage of the present invention is that the reaction mixture maybe formed into a desired shape before the crystallization step, therebyreducing the number of process steps required to prepare catalyticmaterials containing the resulting zeolite. Prior to forming thereaction mixture, it may be necessary to change the liquid content ofthe reaction mixture, either by drying or by adding more liquid, inorder to provide a formable mass which retains its shape. In general,for most shaping methods, water will generally comprise from about 20percent to about 60 percent by weight, and preferably from about 30percent to about 50 percent by weight of the reaction mixture.

The reaction mixture can be formed into a shape, referred to herein as“particles”. Methods for preparing such shapes are well known in theart, and include, for example, extrusion, granulation, agglomerizationand the like. When the shape is in the form of particles, they arepreferably of a size and shape desired for the ultimate catalyst, andmay be in the form of, for example, extrudates, cylinders, spheres,granules, agglomerates and prills. The particles will generally have across sectional diameter between about 1/64 inch and about ½ inch, andpreferably between about 1/32 inch and about ¼ inch, i.e., the particleswill be of a size to be retained on a 1/64 inch, and preferably on a1/32 inch screen and will pass through a ½ inch, and preferably througha ¼ inch screen.

The shape prepared from the reaction mixture will contain sufficientwater to retain a desired shape. Additional water is not required in themixture in order to initiate or maintain crystallization within theshaped reaction mixture. Indeed, it may be preferable to remove some ofthe excess water from the shaped reaction mixture prior tocrystallization. Conventional methods for drying wet solids can be usedto dry the reaction mixture, and may include, for example drying in airor an inert gas such as nitrogen or helium at temperatures below about200° C. and at pressures from subatmospheric to about 5 atmospherespressure.

It should be noted that, while the reaction mixture of the presentinvention is capable of being formed into and retaining a shape, it neednot be shaped prior to formation of the TS-1 crystals. For instance, thereaction mixture may be in the form of a paste-like mass having noparticular shape or profile. Also, the resulting TS-1 product need nothave any particular shape and may, in fact, simply be in the form of apowder.

Zeolite Crystallization

According to the present process, the zeolite is crystallized eitherwithin the reaction mixture or within the shape made from the reactionmixture. In either case, the composition of the mixture from which thezeolite is crystallized has the molar composition ranges stated above.

It is preferred that the total volatiles content of the reaction mixtureduring crystallization be in the range of between about 20 wt. % andabout 60 wt. %, and preferably between about 30 wt. % and about 60 wt.%, based on the weight of the reaction mixture, where the totalvolatiles content is the measure of total volatile liquid, includingwater, in the reaction mixture. It is a feature of the present processthat no additional liquid beyond that required to produce the zeoliteTS-1 is required for zeolite crystallization.

Crystallization of the zeolite takes place in the absence of an addedexternal liquid phase, i.e., in the absence of a liquid phase separatefrom the reaction mixture. In general, it is not detrimental to thepresent process if some liquid water is present in contact with thereaction mixture during crystallization, and it can be expected thatsome water may be on the surface of the reaction mixture duringcrystallization, or that some water may be expelled from the reactionmixture and may collect on or near the reaction mixture as the reactionprogresses. However, it is an objective of the present invention toprovide a method of crystallizing the zeolite in such a way as tominimize the amount of water which must be treated and/or discardedfollowing crystallization. To that end, the present method provides azeolite synthesis method which requires no additional water forcrystallization beyond a sufficient amount of liquid required to formthe zeolite TS-1.

Crystallization is conducted at an elevated temperature and usually inan autoclave so that the reaction mixture is subject to autogenouspressure until the crystals of zeolite are formed. The temperaturesduring the hydrothermal crystallization step are typically maintainedfrom about 90° C. to about 200° C., preferably from about 100° C. toabout 170° C.

The crystallization is conducted under conditions which will preventdehydration of the reaction mixture. This may be accomplished byexposing the reaction mixture to a small amount of water vapor or steamduring crystallization.

The crystallization time required to form crystals will typically rangefrom about 1 hour to about 10 days, and more frequently from about 3hours to about 4 days. Under certain circumstances, crystallizationtimes of less than 24 hours are required to prepare crystallizedmaterial of high crystallinity. In the present method, the crystallizedmaterial collected following the crystallization step will typicallycomprise at least about 50 weight percent crystals. Crystallizedmaterial containing at least about 80 weight percent crystals, and evenat least about 90 weight percent crystals, may also be prepared usingthe present method.

Once the zeolite crystals have formed, the crystals may be water-washedand then dried, e.g., at 90° C. to 150° C. for from 8 to 24 hours. Thedrying step can be performed at atmospheric or subatmospheric pressures.

Due to the unpredictability of the factors which control nucleation andcrystallization in the art of crystalline oxide synthesis, not everycombination of reagents, reactant ratios, and reaction conditions willresult in crystalline products. Selecting crystallization conditionswhich are effective for producing crystals may require routinemodifications to the reaction mixture or to the reaction conditions,such as temperature, and/or crystallization time. Making thesemodifications are well within the capabilities of one skilled in theart.

Seed Crystals

The zeolite made by the present process is crystallized within thereaction mixture, which comprises amorphous reagents. Crystallinematerial (i.e., “seed” crystals of zeolite TS-1) may be added to themixture prior to the crystallization step, and methods for enhancing thecrystallization of zeolites by adding “seed” crystals are well known.However, the addition of seed crystals is not a requirement of thepresent process. Indeed, it is an important feature of the presentprocess that the zeolite can be crystallized within the reaction mixturein the absence of crystals added prior to the crystallization step. Whenseed crystals are used, typically about 0.1% to about 10% of the weightof the silica used in the reaction mixture is added.

Zeolite Crystallite Size

Typically, the crystallite size of the TS-1 made in accordance with thisinvention is less than about 0.2 micron as determined by ScanningElectron Microscopy. As used herein, the term “crystallite size” refersto the longest dimension of the crystal.

The crystallite size of the zeolite may be determined by, for example,grinding the shaped particles to separate the individual crystals. Highresolution electron micrographs of the separated crystals can then beprepared, after which the average size of individual zeolite crystalscan be determined by reference to calibrated length standards. Anaverage crystallite size may then be computed in various well-knownways, including:

${{{Number}\mspace{14mu}{Average}} = \frac{\sum\limits_{i = 1}^{n}\left( {n_{i} \times L_{i}} \right)}{\sum\limits_{i = 1}^{n}n_{i}}},$where n_(i) is the number of zeolite crystals where minimum length fallswithin an interval L_(i). For purposes of this invention, averagecrystal size will be defined as a number average.

It is important to note that for purposes of this invention, zeolitecrystallite size is distinguished from what some manufacturers term“zeolite particle size,” the latter being the average size of allparticles, including both individual crystals and polycrystallineagglomerates, in the as-produced zeolite powder.

Binderless Catalyst

One advantage of the present invention is that the TS-1 catalyst may beprepared in a form that can be used without the necessity of adding abinder to the catalyst. Thus, a shaped TS-1 catalyst can be made withoutthe additional step of adding a binding to the TS-1 and then shaping(e.g., extruding) the bound TS-1. This can be important if the bindersthat would ordinarily be used can be a source of undesirable aluminum.

Thus, the catalysts of the present invention can be in the form of ashaped, binderless catalyst comprising essentially all TS-1 and TS-1precursors. As used herein, the term “TS-1 precursors” refers tocomponents of the reaction mixture, primarily the sources of silica andtitanium oxide and the quaternary ammonium cation, which may remainunreacted in the final product. “Essentially all” refers to the factthat the catalyst is at least 90 weight percent, preferably at least 95weight percent, TS-1 and TS-1 precursors. It should be noted that if thereaction to form the TS-1 crystals is complete and the quaternaryammonium cation is completely removed, the catalyst will compriseessentially all TS-1 with no TS-1 precursors present.

The TS-1 of the present invention is useful in catalysts for oxidationreactions, such as the following:

Oxidation Reactions

The TS-1 prepared by the process of this invention is useful as acatalyst in the oxidation of hydrocarbons. Examples of such reactionsinclude, but are not limited to, the epoxidation of olefins, oxidationof alkanes, and the oxidation of cyclohexane.

The amount of TS-1 catalyst employed is not critical, but should besufficient so as to substantially accomplish the desired oxidationreaction in a practicably short period of time. The optimum quantity ofcatalyst will depend upon a number of factors including reactiontemperature, the reactivity and concentration of the hydrocarbonsubstrate, hydrogen peroxide concentration, type and concentration oforganic solvent, as well as the activity of the catalyst. Typically,however, the amount of catalyst will be from about 0.001 to 10 grams permole of hydrocarbon.

Typically, the titanium-containing crystalline zeolites of thisinvention are thermally treated (calcined) prior to use as a catalyst.

The oxidizing agent employed in the oxidation processes of thisinvention is a hydrogen peroxide source such as hydrogen peroxide (H₂O₂)or a hydrogen peroxide precursor (i.e., a compound which under theoxidation reaction conditions is capable of generating or liberatinghydrogen peroxide).

The amount of hydrogen peroxide relative to the amount of hydrocarbonsubstrate is not critical, but must be sufficient to cause oxidation ofat least some of the hydrocarbon. Typically, the molar ratio of hydrogenperoxide to hydrocarbon is from about 100:1 to about 1:100, preferably10:1 to about 1:10. When the hydrocarbon is an olefin containing morethan one carbon-carbon double bond, additional hydrogen peroxide may berequired. Theoretically, one equivalent of hydrogen peroxide is requiredto oxidize one equivalent of a mono-unsaturated substrate, but it may bedesirable to employ an excess of one reactant to optimize selectivity tothe epoxide. In particular, the use of a small to moderate excess (e.g.,5 to 50%) of olefin relative to hydrogen peroxide may be advantageousfor certain substrates.

If desired, a solvent may additionally be present during the oxidationreaction in order to dissolve the reactants other than the TS-1, toprovide better temperature control, or to favorably influence theoxidation rates and selectivities. The solvent, if present, may comprisefrom 1 to 99 weight percent of the total oxidation reaction mixture andis preferably selected such that it is a liquid at the oxidationreaction temperature. Organic compounds having boiling points atatmospheric pressure of from about 25° C. to about 300° C. are generallypreferred for use. Excess hydrocarbon may serve as a solvent or diluent.Illustrative examples of other suitable solvents include, but are notlimited to, ketones (e.g., acetone, methyl ethyl ketone, acetophenone),ethers (e.g., tetrahydrofuran, butyl ether), nitriles (e.g.,acetonitrile), aliphatic and aromatic hydrocarbons, halogenatedhydrocarbons, and alcohols (e.g., methanol, ethanol, isopropyl alcohol,t-butyl alcohol, alpha-methyl benzyl alcohol, cyclohexanol). More thanone type of solvent may be utilized. Water may also be employed as asolvent or diluent.

The reaction temperature is not critical, but should be sufficient toaccomplish substantial conversion of the substrate hydrocarbon within areasonably short period of time. It is generally advantageous to carryout the reaction to achieve as high a hydrogen peroxide conversion aspossible, preferably at least about 50%, more preferably at least about90%, most preferably at least about 95%, consistent with reasonableselectivities. The optimum reaction temperature will be influenced bycatalyst activity, hydrocarbon reactivity, reactant concentrations, andtype of solvent employed, among other factors, but typically will be ina range of from about 0° C. to about 150° C. (more preferably from about25° C. to about 120° C.). Reaction or residence times from about oneminute to about 48 hours (more desirably from about ten minutes to abouteight hours) will typically be appropriate, depending upon theabove-identified variables. Although subatmospheric pressures can beemployed, the reaction is preferably performed at atmospheric or atelevated pressure (typically, between one and 100 atmospheres),especially when the boiling point of the hydrocarbon substrate is belowthe oxidation reaction temperature. Generally, it is desirable topressurize the reaction vessel sufficiently to maintain the reactioncomponents as a liquid phase mixture. Most (over 50%) of the hydrocarbonsubstrate should preferably be present in the liquid phase.

The oxidation process of this invention may be carried out in a batch,continuous, or semi-continuous manner using any appropriate type ofreaction vessel or apparatus such as a fixed bed, transport bed,fluidized bed, stirred slurry, or CSTR reactor. The reactants may becombined all at once or sequentially. For example, the hydrogen peroxideor hydrogen peroxide precursor may be added incrementally to thereaction zone. The hydrogen peroxide could also be generated in situwithin the same reactor zone where oxidation is taking place.

Once the oxidation has been carried out to the desired degree ofconversion, the oxidized product may be separated and recovered from thereaction mixture using any appropriate technique such as fractionaldistillation, extractive distillation, liquid-liquid extraction,crystallization, or the like.

Olefin Epoxidation

One of the oxidation reactions for which TS-1 is useful as a catalyst isthe epoxidation of olefins. The olefin substrate epoxidized in theprocess of this invention may be any organic compound having at leastone ethylenically unsaturated functional group (i.e., a carbon-carbondouble bond) and may be a cyclic, branched or straight-chain olefin. Theolefin may contain aryl groups (e.g., phenyl, naphthyl). Preferably, theolefin is aliphatic in character and contains from 2 to about 30 carbonatoms. The use of light (low-boiling) C₂ to C₁₀ mono-olefins isespecially advantageous.

More than one carbon-carbon double bond may be present in the olefin,i.e., dienes, trienes and other polyunsaturated substrates may be used.The double bond may be in a terminal or internal position in the olefinor may alternatively form part of a cyclic structure (as in cyclohexene,for example).

Other examples of suitable substrates include unsaturated fatty acids orfatty acid derivatives such as esters or glycerides, and oligomeric orpolymeric unsaturated compounds such as polybutadiene. Benzylic andstyrenic olefins may also be epoxidized, although the epoxides ofcertain styrenic olefins such as styrene may further react or isomerizeunder the conditions utilized in the present invention to form aldehydesand the like.

The olefin may contain substituents other than hydrocarbon substituentssuch as halide, carboxylic acid, ether, hydroxy, thiol, nitro, cyano,ketone, acyl, ester, anhydride, amino, and the like.

Exemplary olefins suitable for use in the process of this inventioninclude ethylene, propylene, the butenes (i.e., 1,2-butene, 2,3-butene,isobutylene), butadiene, the pentenes, isoprene, 1-hexene, 3-hexene,1-heptene, 1-octene, diisobutylene, 1-nonene, 1-tetradecene,pentamyrcene, camphene, 1-undecene, 1-dodecene, 1-tridecene,1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene,1-nonadecene, 1-eicosene, the trimers and tetramers of propylene,styrene (and other vinyl aromatic substrates), polybutadienes,polyisoprene, cyclopentene, cyclohexene, cycloheptene, cyclooctene,cyclooctadiene, cyclododecene, cyclododecatriene, dicyclopentadiene,methylenecyclopropane, methylenecyclopentane, methylenecyclohexane,vinyl cyclohexane, vinyl cyclohexene, methallyl ketone, allyl chloride,the dichlorobutenes, allyl alcohol, allyl carbonate, allyl acetate,alkyl acrylates and methacrylates, diallyl maleate, diallyl phthalate,unsaturated triglycerides such as soybean oil, and unsaturated fattyacids, such as oleic acid, linolenic acid, linoleic acid, erucic acid,palmitoleic acid, and ricinoleic acid and their esters (including mono-,di-, and triglyceride esters) and the like.

Olefins which are especially useful for epoxidation are the C₂-C₃₀olefins having the general structureR³R⁴C═CR⁵R⁶wherein R³, R⁴, R⁵ and R⁶ are the same or different and are selectedfrom the group consisting of hydrogen and C₁-C₂₀ alkyl.

Mixtures of olefins may be epoxidized and the resulting mixtures ofepoxides either employed in the mixed form or separated into thedifferent component epoxides.

EXAMPLES

There are numerous variations on the embodiments of the presentinvention illustrated in the Examples which are possible in light of theteachings supporting the present invention. It is therefore understoodthat within the scope of the following claims, the invention may bepracticed otherwise than as specifically described or exemplified.

Example 1 Preparation of Titanosilicate Zeolite TS-1 Using Ti(butoxide)₄

A reaction mixture was prepared by placing 100 grams of Ultrasil® VN3SPsilica in a Baker-Perkins mixer. Sixty-five grams of 40 wt. %tetrapropylammonium hydroxide (TPAOH) was added to the mixer and mixedwith the silica for 30 minutes. Eight grams of Ti(butoxide)₄ wasdissolved in 20 grams of isopropyl alcohol and added to the mixer,followed by 35 grams of water. The mixture was then mixed until auniform paste was obtained. It is important that the Ti(butoxide)₄ bethoroughly dispersed throughout the paste. No binder is added to thepaste.

The paste was dried to an extrudable consistency and extruded with aCarver press using a 1/12 inch die. Half of the extrudate was dried to47% volatiles, and the other half was dried to 43% volatiles.

Both batches were crystallized in an autoclave at autogenous pressure at150° C. for 24 hours. The resulting products were binderless extrudatescontaining essentially 100% titanosilicate zeolite TS-1 as determined byX-ray diffraction analysis and infra-red spectroscopy (as described inaforementioned U.S. Pat. No. 4,410,501). The extrudates containedcrystals of TS-1 having a crystallite size of less than about 0.2micron, as determined by Scanning Electron Microscopy.

Example 2 Preparation of Titanosilicate Zeolite TS-1 Using Ti(butoxide)₄

Titanosilicate zeolite TS-1 was prepared by the procedure of Example 1,except that the Ti(butoxide)₄ was mixed with the TPAOH (withoutisopropyl alcohol) prior to addition to the mixer. The resulting productwas binderless extrudates containing essentially 100% titanosilicatezeolite TS-1 as determined by X-ray diffraction analysis and infra-redspectroscopy (as described in aforementioned U.S. Pat. No. 4,410,501).The extrudates contain crystals of TS-1 having a crystallite size ofless than about 0.4 micron, as determined by Scanning ElectronMicroscopy (“SEM”).

1. A method for preparing crystalline titanosilicate zeolite TS-1, saidmethod comprising: a. preparing a reaction mixture comprising at leastone active source of silica and at least one hydrolysable titaniumcompound in amounts sufficient to produce zeolite TS-1, and sufficientwater to shape said mixture; b. forming said reaction mixture into ashape; and c. heating said reaction mixture under crystallizationconditions and in the absence of an added external liquid phase forsufficient time to form crystals of zeolite TS-1.
 2. The methodaccording to claim 1 wherein the amount of water is sufficient to makethe reaction mixture self-supporting.
 3. The method according to claim 1wherein said reaction mixture has a water/silica molar ratio duringcrystallization of no greater than about
 3. 4. The method of claim 3wherein said reaction mixture during crystallization has a water/silicamolar ratio between about 0.7 and about
 2. 5. The method according toclaim 1 wherein said reaction mixture has the following molarcomposition ranges: SiO₂/TiO₂ =  25-500 OH⁻/SiO₂ = 0.04-0.30 H₂O/SiO₂ =0.5-3   Q/SiO₂ = 0.04-0.30

where Q is a quaternary ammonium cation.
 6. The method according toclaim 5 wherein said reaction mixture has the following molarcomposition ranges: SiO₂/TiO₂ =  30-150 OH⁻/SiO₂ = 0.06-0.15 H₂O/SiO₂ =0.7-2   Q/SiO₂ =  0.06-0.15.


7. The method according to claim 5 wherein the quaternary ammoniumcation is a tetraalkylammonium cation.
 8. The method according to claim7 wherein the tetraalkylammonium cation is a tetrapropylammonium cation.9. The method according to claim 1 wherein the crystals of zeolite TS-1are spherical or cylindrical particles having a cross sectional diameterbetween about 1/64 inch and about ½ inch.